Two boys, ages 14 and 16, were charged with having a weapon on school grounds after they brought BB guns to school, Sgt. Ryan Flogstad said. They were released to their parents.

A third boy, age 15, was also charged with having a weapon on school grounds, but was not as cooperative as the others, police spokesman Sam Clemens said.

The boy allegedly punched staff members and kicked a police officer who responded to the school, Clemens said. He was charged with simple assault and simple assault on law enforcement and was taken to the juvenile detention center.

A letter to parents from the Sioux Falls School District said the boys brought the BB guns to trade or sell them. Clemens said none of the boys threatened anyone, but bringing the weapons still constituted a crime.

"The kids know they're not supposed to have them," he said, noting that Sioux Falls schools occasionally see kids bring weapons like knives. "This isn't an isolated incident."